> > > > How did you finally end up testing the error case. Want to simualate
> > > > error aritificially and test it.
> > > >
>
> I used the blockdev error injection layer. It only works with ext2, because
> ext4 (and other filesystems) will error and go into readonly.
>
> dd if=/dev/zero of=/tmp/loop bs=1M count=100
> losetup /dev/loop8 /tmp/loop
> mkfs.ext2 /dev/loop8
> mount -o errors=continue /dev/loop8 /mnt/loop/
> mkdir -p /mnt/loop/{upperdir,workdir}
> mount -t overlay -o volatile,index=off,lowerdir=/root/lowerdir,upperdir=/mnt/loop/upperdir,workdir=/mnt/loop/workdir none /mnt/foo/
> echo 1 > /sys/block/loop8/make-it-fail
> echo 100 > /sys/kernel/debug/fail_make_request/probability
> echo 1 > /sys/kernel/debug/fail_make_request/times
> dd if=/dev/zero of=/mnt/foo/zero bs=1M count=1
> sync
>
> I tried to get XFS tests working, but I was unable to get a simpler repro than
> above. This is also easy enough to do with a simple kernel module. Maybe it'd be
> neat to be able to inject in errseq increments via the fault injection API one
> day? I have no idea what the VFS's approach here is.
>
Here you go. A simple xfstest:
https://github.com/amir73il/xfstests/commits/ovl-volatile
It passes with check -overlay on xfs/ext4 and it fails if you uncomment
the -o volatile mount option
Just move it to the tests/overlay/ tests and add syncfs (I wasn't sure
about how to do that).
Thanks,
Amir.
